The present invention relates to a vehicle brake device and a method of controlling the vehicle brake device, and more particularly, to a vehicle brake device that includes hydraulic brakes and a regenerative brake generating a regenerative brake force and divides a braking force into a hydraulic brake force and a regenerative brake force.
In the past, a vehicle brake device, which includes a hydraulic brake generating a hydraulic brake force by using hydraulic pressure generated according to the driver's operation of a brake and a regenerative brake generating a regenerative brake force and performs regenerative cooperation by dividing a braking force into the hydraulic brake force and the regenerative brake force, has been known as a vehicle brake device.
An object of a regenerative brake, which is used in this kind of vehicle brake device, is to convert the kinetic energy of the wheels during braking into electric energy and to use energy effectively. However, the maximum regenerative brake force which can be regenerated by the regenerative brake, has a limitation due to the speed of a vehicle during braking, the charge state of a battery, or the like. For this reason, even in terms of the effective use of energy, it is preferable that a ratio of the regenerative brake be increased by the change of a ratio between a braking force which is generated by the hydraulic brake, and a braking force which is generated by the regenerative brake, according to the maximum regenerative brake force even while the hydraulic brake is performing braking.
In order to achieve this, various methods of performing regenerative cooperation have been proposed. However, when a ratio of the regenerative brake in terms of a braking force is changed, a driver might feel a sense of discomfort in the brake feeling. For this reason, as means for obtaining a comfortable brake feeling, there is a vehicle brake device that makes brake fluid escape into a low pressure accumulator through a pressure reducing valve when performing braking using a regenerative brake and pumps brake fluid from the accumulator using a motor pump unit, which is electrically controlled, when increasing hydraulic pressure (for example, see Patent Document 1).